Abstract
We derive a renormalized classical spin (RCS) theory for S > 1/2 quantum magnets by constraining a generalized classical theory that includes all multipolar fluctuations to a reduced CP1 phase space of dipolar SU(2) coherent states. When the spin Hamiltonian Ĥ(S) is linear in the spin operators Ŝj for each lattice site j, the RCS Hamiltonian H͂cl coincides with the usual classical model Hcl = limS→∞ Ĥ(S). In the presence of nonlinear terms, however, the RCS theory is more accurate than Hcl. For the many materials modeled by spin Hamiltonians with (nonlinear) single-ion anisotropy terms, the use of the RCS theory is essential to accurately model phase diagrams and to extract the correct Hamiltonian parameters from neutron-scattering data.
| Original language | English |
|---|---|
| Article number | 134432 |
| Journal | Physical Review B |
| Volume | 112 |
| Issue number | 13 |
| DOIs | |
| State | Published - Oct 17 2025 |
Funding
We thank Martin Mourigal and Xiaojian Bai for helpful discussions. This work was funded by the U.S. Department of Energy, Office of Science, 631 Office of Basic Energy Sciences, under Award No. DE-SC-DE-SC-0018660. K.B. and H.Z. acknowledge support from the LANL LDRD program. Z.L. (phase diagram of Fig. 1) acknowledges support from U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Science and Engineering Division. D.M.P. acknowledges support by the DOE Office of Science (Office of Basic Energy Sciences). The authors of this paper were supported by UT-Battelle, LLC, under Contract No. DEAC05-00OR22725 with the U.S. Department of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this paper, or allow others to do so, for U.S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan [40].